Gaseous electric discharge lamp device



Oct 1939 w. UYTERHOEVEN GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Filed May10, 1958 Fig. 2

INVENTOR n m df 11 W m AT ORNEY Patented Oct. 31, 1939 GASEOUS ELECTRICDISCHARGE LAMP DEVICE Willem Uyterhoeven, Eindhoven, Netherlands, as-

signor to General Electric Company, a corpo ration of New YorkApplication May 10, 1938, Serial No. 207,081 In Germany May 14, 1937 5'Claims. (01. 176-122) The present invention relates to gaseous electricdischarge lamp devices generally and more particularly the inventionrelates to such devices which operate at elevated container temperaturesand which are mounted in a heat conservator, such as a sealed envelope,

The light emitted by lamp devices of this type is deficient in rays ofcertain wave length and it has been proposed heretofore to provide aluminescent material capable of being excited by radiation from saidlamp device to emit visible light which complements and supplements thelight emitted by said discharge lamp. Preferably the luminescentmaterial is applied to the inner surface of the envelope and a lamp unitof this type is described in co-pending applicatlon Serial Number163,850, filed September 14, 1937, assigned to the assignee of thepresent application. I have observed that in lamp units of this type thelight emitted by the luminescent material diminishes rapidly duringoperation of the discharge lamp device to lower the eiiiciency of thelamp unit. I have discovered that this loss in efficiency is due to thedeterioration of the luminescent material under the heat emitted by thedischarge lamp device.

The object of the present invention is to provide a lamp unit of theabove type in which the luminescent material retains its light emittingcapacity for a long useful operating life of the lamp unit. Stillfurther objects and advantages attaching to the device and to its useand operation will be apparent to those skilled in the art from thefollowing particular description.

The invention attains its objects by surrounding the gaseous electricdischarge lamp device by a gas having heat absorbing properties, such ascarbon dioxide or nitrogen, at such pressure that convection currentscan occur in the gas during the operation of the device and by providingthe envelope with a heat radiating part at which the heat absorbed bysaid gas is dissipated. The pressure of the gas should be a substantialone since the cooling effect of the convection currents in the gasvaries directly as the square of the gas pressure. The heat dissipatingpart of the envelope is separated from that part of the envelope onwhich the luminescent material is applied and through which the lightfrom the lamp device and the luminescent material passes. A lamp unithaving this structure retains its initial efficiency for a long usefulop- Fig. 2 is a front elevational, partly sectional view of anotherembodiment of the invention.

Like numbers denote like parts in both the figures.

Referring to Fig. -1 the gaseous electric discharge lamp devicecomprises a tubular container I, such as a quartz container, having aninner diameter of about 4 mm. and having sealed therein thermionic,activated electrodes 2 and 3 of the type which are heated to an electronemitting, arc discharge supporting temperature by the discharge incidentthereat. Said electrodes 2 and 3 are separated a distance of about 18mm. The container i has therein a starting gas, such as argon, at apressure of about 10 to 20 mm. and a quantity of mercury. Mercury vapordischarge devices of this type are capable of operation with vaporpressures of 10 atm. and

7 higher and preferably the vapor pressure therein during the operationthereof is about 20 atm. The discharge device is mounted in a. heatconservator having a; tubular part 4. Said tubular member 4 consists ofvitreous material capable of transmitting visible and ultra violetlight, such as Corex glass, and has a press 6 at one end thereof intowhich the current leads I and 8 of the discharge device are sealed. Thespace 5 in the tubular part 4 is filled with nitrogen atv a pressure ofabout 10 cm. at room temperature.

The bulbous part 9 of the heat conservator is fused to the tubularmember 4 between the press 6 and the upper end of the discharge deviceso that the upper part of the tubular member 4 is not enclosed by saidbulb 9. The inner surface of the bulb 9 has a coating l0 thereon ofluminescent material, such as zinc sulphide, which is light emittingunder. excitation by radiation from the discharge lamp. Preferably thespace between the bulb 9 and the tubular member 4 is evacuated.

During the operation of the discharge device strong convection currentsare set up in the gas in the tubular member 4. These currents carry heataway from the container i upward to the exposed part of the tubularmember 4 where it is dissipated. Thus the amount of heat from thecontainer I which strikes the wall of the envelope 9 is considerablyless than would be the case were the gas in the tubular member 4, andthe tubular member 4 itself omitted. Consequently the temperature of theluminescent coating I0 is considerably lower in the lamp unit describedabove than in prior devices and the luminescent material retains itslight emitting power undiminished, for a long, useful operating life.

The gaseous electric discharge lamp device 11- lustrated in Fig. 2 ofthe drawing is similar to that shown in Fig. 1 except that in thisembodiment the tubular member 4 is omitted and the bulb 9 is providedwith a neck I5 which has cemented thereto, in the usual manner, abayonet base l2 having the two contacts l3 and N thereof connected tothe current leads I and 8 of the discharge lamp device. The bulb 9, I5is filled with a heat absorbing gas, such as nitrogen, at a pressure ofabout 50 cm. and the neck [5 of the bulb 9, I5 is an elongated one ofrelatively large area. During the operation of the device the strongconvection currents set up in the gas in the bulb 9 carry heat from thedischarge lamp up into the neck I5 where it is dissipated by the gascoming into contact with the inner surface of the neck I5. The coolergas then flows downward (as shown by the arrows and dotted lines II inthe drawing) along the coated inner surface of the bulb 9. It isadvantageous, therefore, that the heat dissipating capacity of the neckl5 be as large as is consistent with the maintainance of the operatingtemperature of the container I so that the luminescent coating Hi can bemaintained at a temperature lower than that which would causedeleterious changes in the said luminescent coating ID. The heatdissipating capacity of the neck I5 is increased by omitting theluminescent coating ill from the inner surface of the neck l5. Whendesired, other means for increasing the heat dissipating capacity of theneck [5 can be used in addition to the omission of the coating ID fromthe said neck I5; for example, the neck I 5 is made of a glass which hasa greater heat radiating capacity than the glass of which the sphericalpart of the bulb consists, when desired; or the outside surface of theneck I5 is roughened or coated 'with a material, such as carbon, whichradiates heat strongly, when desired, or all these expedients are usedin combination, when desired.

It will be understood, of course, that we contemplate combining all thestructural details of both the devices illustrated in the drawing whichmay be desirable in extreme cases, for example, when the discharge lampgenerates a great quantity of heat and the particular luminescentmaterial used is of a kind strongly affected by heat. Other means forincreasing the heat dissipating capacity of the heat dissipating part ofthe envelope can be used, when desired, for example, metal fins or watercooling mechanisms.

While I have shown and described and have pointed out in the annexedclaims certain novel features of the invention, it will be understoodthat various omissions, substitutions and changes in the forms anddetails of the device illustrated and in its use and operation may bemade by those skilled in the art without departing from the broad spiritand scope of the invention.

What I claim as new and desire to secure by .Letters Patent of theUnited States, is:

1. An electric lamp comprising in combination a gaseous electricdischarge lamp device of the type operating with an elevated containertemperature, aheat conservator in which said lamp device is mounted,said conservator having a heat dissipating part, a coating of heatsensitive, luminescent material in said conservator in light receivingrelation to said lamp device and remote from said heat dissipatingconservator part and a. gaseous filling in said conservator at apressure such that the heat emitted by said lamp device during theoperation thereof causes convection currents in said gas to transfer theheat from said lamp to the heat dissipating part of said conservator toincrease the useful life of said material.

2. An electric lamp comprising in combination a gaseous electricdischarge lamp device of the type operating with an elevated containertemperature, a heat conservator in which said lamp device is mounted,said conservator having a heat dissipating part, a coating of heatsensitive, luminescent material in said conservator in light receivingrelation to said lamp device and remote from said heat dissipatingconservator part and an infra-red ray absorbing gas in said conservatorat a pressure such that the heat emitted by said lamp device during theoperation thereof causes convection currents in said gas to transfer theheat from said lamp to the heat dissipating part of said conservator toincrease the useful life of said material.

3. An electric lamp comprising in combination a gaseous electricdischarge lamp device of the type operating with an elevated containertemperature, a heat conservator in which said lamp device is mounted, acoating of heat sensitive, luminescent material in said conservator inlight receiving relation to said lamp device and a gaseous filling insaid conservator at a pressure such that the heat emitted by said lampdevice during the operation thereof causes convection currents in saidgas to transfer the heat from said lamp to a heat dissipating part ofsaid conservator removed from said luminescent material to increase theuseful life of said material, the heat dissipating part of saidconservator having a greater heat dissipating capacity per unit of areathan the other parts of said conservator.

4. An electric lamp comprising in combination a gaseous electricdischarge lamp device of the type operating with an elevated containertemperature, a heat conservator in which said lamp device is mounted,said heat conservator consisting of a tubular member and a bulbousmember, said tubular member being partially surrounded by said bulbousmember, said lamp device being mounted in the part of said tubularmember surrounded by said bulbous member, a coating of heat sensitive,luminescent material on the inner surface of said bulbous member and agaseous filling in said tubular member at a pressure such that the heatemitted by said lamp device during the operation thereof causesconvection currents in said gas to transfer heat from said lamp deviceto the exposed part of said tubular member to increase the useful lifeof said luminescent material.

5. An electric lamp comprising in combination a gaseous electricdischarge lamp device of the type operating with an elevated containertemperature, a heat conservator in which said lamp device is mounted,said heat conservator consisting of a tubular member and a bulbousmember, said tubular member being partially surrounded by said bulbousmember, said lamp device being mounted in the part of said tubularmember surrounded by said bulbous member, a coating of heat sensitive,luminescent material on the inner surface of said bulbous member and agaseous filling in said tubular member at a pressure such that the heatemitted by said lamp device during the operation thereof causesconvection currents in said gas to transfer heat from said lamp deviceto the exposed part of said tubular member to increase the useful lifeof said luminescent material, the exposed part of said tubular memberhaving a greater heat dissipating capacity per unit of area than thebulbous part of said conservator.

wnmm UYTERHOEVEN.

